The electrical connection box described in Japanese Patent Application Publication No. JP-2004-040873-A (FIG. 6) has been known for some time as an electrical connection box that is mounted in an automobile. It discloses a circuit board on which an electrical circuit is formed and which is positioned in a case. On a lower portion of a side wall of the case, a portion that bulges outward is formed which includes a connector. Within the connector accommodation portion, a connector that is open at the bottom is included.
With this kind of electrical connection box, water that forms on the top side (as a result of dewing or the like) sometimes flows down along an outer side face of a side wall of the case. Water that flows down the side wall reaches the connector accommodation portion, then flows farther down and reaches the bottom edge of the connector accommodation portion. Because the connector is open at the bottom edge of the connector accommodation portion, there is concern that the water might penetrate into the case via the opening and short out the electrical circuit, which makes up a circuit assembly.